The invention relates generally to cylinders for the pressure and heat treatment of materials, and more particularly to a cylinder having improved deflection control.
Deflection-controlled cylinders are predominantly used for the pressure and temperature treatment of webs of paper, nonwoven material, plastic film and textiles, although they are certainly not limited to these uses. Such cylinders are formed from a stationary crosshead surrounded by a rotatable hollow cylinder that is supported against the crosshead. The crosshead can flex within the hollow cylinder via a suitable hydraulic device. In the case of normal, solid cylinders, the counter-forces exerted against the line load caused in the cylinder nip by the line force are created along with a deflection of the cylinder. In deflection-controlled cylinders, this deflection is transferred to the crosshead, so that the hollow cylinder remains independent thereof and can undergo whatever deflection profile is desired. In particular, the hollow cylinder can remain straight.
In a number of applications, it is necessary to drive the hollow cylinder. The drive raises significant design problems, because in certain cases the hollow cylinder can be displaced in the radial direction, and may also demonstrate alignment errors relative to an axis fixed to the housing that result from deflection. Therefore, the working surface of the drive at the hollow cylinder does not have a well-defined position, either with respect to the machine frame or, in particular, with respect to the crosshead, which flexes under stress. It must be noted that the drives, particularly for cylinders in the paper industry which can have a length of up to ten meters and a diameter of up to one meter, must transfer significant power, at equally significant rotational speeds that are on the order of a thousand meters per minute or more. An imprecise gear engagement will take its toll very quickly in the form of excessive wear.
In order to eliminate the effects of the change in position of the ends of the hollow cylinder on the engagement of a drive pinion, it is known to mount the pinion on a coaxial projection of the hollow cylinder in a drive housing. The drive housing and the pinion thus move with the end of the hollow cylinder, but maintain their reciprocal position and their proper engagement.
U.S. Pat. No. 3,766,620 discloses an example of this configuration, in which the end of the hollow cylinder is mounted on the crosshead in a roller bearing and the displacement of the end of the hollow cylinder relative to the crosshead is therefore limited to alignment errors. The gear housing surrounds the projection, which has a smaller outer diameter than the hollow cylinder. An axial flange connected with the gear housing engages with the projection from the radially outward direction. Between the outer diameter of the axial flange and the inner diameter of the projection, a double-roller bearing is arranged, on which the gear housing, which does not rotate, is supported on the rotating projection. Radially outside the projection a drive journal is mounted with its axis parallel to the gear housing, on which a drive pinion is seated. The drive journal engages with a gearing located on the outside of the projection at the level of the inner bearing of the drive housing.
However, the means by which the gear housing is mounted is not very advantageous because the support length is limited to the width of the double-roller bearing, and significant torque is exerted on this bearing due to forces acting when the gear housing is angled relative to the hollow cylinder.
German Pat. Nos. 25 07 677 and 36 23 028 disclose deflection-controlled cylinders in which the hollow cylinders are not mounted on the crosshead at their ends, but rather which can be displaced radially relative to the crosshead, as a whole, along corresponding guides. The overall displacement of the ends of the hollow cylinder with which the drives engage is therefore even greater, because in addition to the purely angular change, there is also a translational displacement. In German Pat. No. 25 07 677, a drive housing with a pinion on both sides thereof is mounted on the outside of a projection of the hollow cylinder. A cylinder of this type, with some design changes, is also disclosed in German Pat. No. 36 23 028, in which the drive journal carrying the pinion is formed as a hollow journal, which has a spiral-toothing gearing on the inside, and into which engages a corresponding spiral-toothed gearing disposed at the end of a drive shaft. In the first two of the above-mentioned references, the displacement of the drive housing was compensated for by a drive via a double-jointed power source. In the last-mentioned reference, the drive shaft with the spiral-toothed gearing performs this task.
The features common to the cylinders mentioned above are that the drive housing is mounted exclusively on the projection of the hollow cylinder, and that the hollow cylinder is guided within bearings or straight guides arranged therein, which engage with the crosshead.
German Pat. No. 36 45 034 discloses a hollow cylinder mounted on the crosshead in which the bearing, in contrast to the cylinder disclosed in U.S. Pat. No. 3,766,620, is seated on the outside of the projection and supported on the inner circumference of a bearing bell, which is arranged without play on a supporting extension at the outer end of the crosshead that has a reduced diameter. This reference indicates that one form of the drive may include a chain gear ring connected to the front side of the hollow cylinder. Such an "open" drive cannot be used in many applications because it is disruptive, simply in terms of design, to the working area of the cylinders located between the machine supports.